At the present stage of the art, laser fusion D-T pellets are commercially available as well as laser train and target chambers. Reported yields from laser fusion thermonuclear reactions from both Lawrence Livermore Laboratory and KMS Fusion exceed neutron radiation levels of 10.sup.7. Russian reports indicate several years of successful operation with pulsed reactors with peak fluxes during 0.5 microsecond bursts in the 10.sup.16 n/cm.sup.2 -sec. range using five to 50 pulses per second.
Many patents have issued in the U.S.A. and abroad in the fusion field. Representative publications are:
(1) Research/Development, May 1975, Vol. 26, No. 5, pages 55ff., "Thermonuclear fusion research with high power lasers";
(2) Nuclear Technology, Vol. 22, April 1974, pp 36ff., "The relevance of various neutron sources to fusion-reactor radiation effects";
(3) Plasma Physics and Controlled Nuclear Fusion Research, 1974, Vol. II, "Experimental Study of Laser-Driven Compression of Spherical Glass Shells";
(4) Laser Focus, September 1975, pp 39ff., "More Evidence that Fusion Works".
The usual thermochemical water splitting processes and like other chemical disassociation processes are characterized by practical limitations on the temperature and free energy changes of at least some individual reaction steps.
For any thermal process with an energy absorption at a high temperature T.sub.H, and an energy release at a low temperature T.sub.c, the minimum positive entropy change as set forth for example, by B. M. Abraham and F. Schreiner, in Ind. Eng. Chem. 13, 305 (1974), in the high temperature step of a two step process, is: ##EQU1## For non-pyrochemical processes, i.e., where T.sub.H .ltoreq.1000.degree. C., using EQU .DELTA.G.sub.f.sup.o (H.sub.2 O,l)=-56,690 cal/gmole
for the reaction EQU H.sub.2 +1/2O.sub.2 .fwdarw.H.sub.2 O(l)
and assuming that T.sub.C =300.degree. K., from EQN (1), EQU .DELTA.S.sub.H .gtoreq.58.3 cal/gmole.degree.K. (e.u.).
Since .DELTA.S for most conventional thermochemical reactions is 30 to 40 e.u., it is not likely that a two step cycle to split water can be found if one is constrained to use chemical processes which must then divide the entropy change among several processing steps. As a result, multiple low and intermediate thermochemical reaction steps must be used to achieve large total free energy changes and total entropy changes which equal the sum required. Because of temperature restrictions on vessels and other materials through which reaction heat must be transferred, it is generally accepted by persons skilled in the current state of the chemical processing art that the maximum economically attainable Gibbs free energy change for any single thermochemical reaction step is in the range of 10 to 20 kcal/mole.
This generalization can be understood from thermodynamic principles when we recognize that for usual temperatures .DELTA.S.sub.H .ltoreq.20 e.u. and EQU .DELTA.G=.DELTA.H-T.DELTA.S.
It is commonly the case that .DELTA.H is a slowly varying function of the temperature so that, neglecting any variation in .DELTA.H, the maximum reduction in .DELTA.G accomplished by raising the temperature from 298.degree. K. to 1273.degree. K. is less than or equal to about 19.5 kcal/gmole.
Furthermore, even where the energy change required in the individual reaction steps is sufficiently low the rates of reaction for the individual process steps are often too slow at normal thermochemical temperatures or the heat energy applied takes considerable time to heat the chemicals being reacted the process may not be economically viable.